Toxicological effects of microplastic fibers from different disposable face masks on Caenorhabditis elegans

During the COVID-19 pandemic, the widespread use of disposable face masks generated substantial waste, much of which ends up in terrestrial environments. However, the impact of this discarded material on soil ecosystems remains poorly understood. This study investigated the toxicological effects of microplastics derived from three types of disposable face masks (KF94, medical, and particulate respirator) and a polypropylene reference material on the soil nematode Caenorhabditis elegans (C. elegans). Exposure to 0.3 % (w/w, microplastic/soil) microplastics from KF94 masks and particulate respirators significantly reduced offspring numbers. Mass spectrometry (MS)-based metabolomic analysis revealed distinct metabolic alterations in C. elegans exposed to microplastics. Both KF94 masks and particulate respirators commonly disrupted the polyamine biosynthesis pathway but exhibited differing impacts on associated metabolites. High-resolution MS analysis of plastic additives extracted from the masks suggested that these differential metabolic changes could be attributed to various additives, including phthalates known to exhibit reproductive toxicity in C. elegans. These findings highlight the potential risk of plastic additives from disposed face masks disrupting soil ecosystems, raising concerns about their long-term environmental impact on soil health and biodiversity.